1. Field of the Invention
The present invention relates to anti-theft devices for oil/gas well Christmas tree structures. Even more particularly, the present invention relates to a well Christmas tree guard apparatus which prevents removal of the well Christmas tree from its position at the well head by denying access to the bolted flanged connection which connects the Christmas tree to the remainder of the gas or oil well.
2. General Background and Prior Art
In the oil and gas industry, it is well known that the upper most portion of a well as it leaves the surface of the ground is provided with a structure known in the art as a "Christmas tree." The Christmas tree is generally an assembly of valves, tees, crosses, and other fittings at the well head used to control oil or gas production and to give access to the well tubing. Other fittings such as choke jackets, pressure guages, and the like, can become part of what is known in the art as the "Christmas tree."
This assembly of valves, tees and other fittings which is affixed to the gas well or oil well at the well head is generally attached to the well head by means of a flanged bolted connection.
This merely refers to a connection in which two flanged members (usually circular in shape) are abutted together in a face-to-face relationship, with each flange member having a plurality of peripheral holes which are aligned during assembly to provide a plurality of aligned openings through which bolted connections can be made. These nut and bolt fasteners are placed through the holes and tightened and the connection is perfected by means of a torque wrench or the like so that no leakage occurs. Many times, a master valve is provided on the Christmas tree which controls the flow of gas or oil directly from the well itself. This valve can be closed, preventing any flow of well to the Christmas tree itself. When the master control valve is closed, the Christmas tree can be entirely removed by disassembling one of the bolted connections above the master valve itself on the Christmas tree. Since many oil fields are in remote areas where adequate security is often not possible, and because the bolted connections are easily disassembled, the expensive Christmas tree structure is highly susceptible to theft by persons having some skill in piping, or generally some experience in oil or gas field work.
The thieves could in removing a Christmas tree use a truck equipped with an air compressor and proper power tools. In a remote oil field, the bolted connection could quickly be broken and the Christmas tree hoisted on to the truck and removed with the entire theft being undetected in most cases. The owner of the well who is victimized in such a way not only loses the price of the Christmas tree itself, but is further faced with the cost of installing a new Christmas tree in its proper position, and he loses valuable production of oil or gas while the well itself is shut down.
Other valuable type piping devices such as very expensive valves, are faced similarly with the problem as above described with respect to oil or gas well Christmas trees. Many times, a very expensive control valve could be mounted on a pipeline itself, and could be easily removed by unbolting as is the case with the Christmas tree structure. These valves and contollers are quite expensive, and their removal likewise brings a loss of production or supply of oil or gas flowing with the pipeline.
It is to this general problem that the present invention is directed.
Several locking type devices have been patented which have attempted to solve the problem generally of preventing the removal of a bolt from a nut and thus, securing in a locking manner a bolted connection. None of the prior art devices, however, solves the problems and shortcomings which have plagued the prior art and which problems are solved by the present invention in a simple, inexpensive and effective manner.
Most prior art devices which have been patented relate generally to the problem of providing a locking assembly for a nut or bolt on an individual bolted connection. U.S. Pat. No. 3,295,579 entitled "Lock Bolt" and assigned to Allis Chalmers Manufacturing Company of Milwaukee, Wis. shows such a locking assembly for an individual bolt.
U.S. Pat. No. 3,600,914 entitled "Theft Prevention Device for Tractor Drawn Trailers" shows a prior art type locking device for tractor trailer trucks to prevent their theft.
U.S. Pat. No. 3,930,432 entitled "Fastening Assembly" provides a protective cover over a bolted connection. A cap and base element are provided which can be welded together marginally to prevent access to the bolt head itself.
U.S. Pat. No. 3,696,646 also shows an assembly for locking a single nut or bolt to resist unwanted removal.
These prior art devices unfortunately require that a separate locking mechanism be provided for each individual bolt. This method of locking each individual bolt can become quite expensive and time consuming when attempting to solve the problem presented above and as solved by the present invention. Many bolted flanged connections in piping require as many as twelve (12) or more bolts to complete a bolted connection. The number of bolts is, of course, a function generally of the diameter of the flanged connection.
It is therefore an object of the present invention to provide a guard apparatus having an overall structure which protectively encapsulates an entire bolted connection portion of a piping system denying access to the bolts in the bolted connection.
It is another object of the present invention to provide and oil/gas well Christmas tree guard apparatus having an overall structure which protectively encapsulates an entire bolted connection portion of an oil well Christmas tree apparatus denying access to the bolts in the bolted connection.
It is a further object of the present invention to provide a Christmas tree guard apparatus which is simple, economical, and easy to construct.
It is another object of the present invention to provide a Christmas tree guard apparatus which provides a pair of hingedly connected guard halves which can assemble and disassemble for quick placement or removal from a selected Christmas tree flanged connection.
It is another object of the present invention to provide a Christmas tree guard apparatus wherein the latching and hinge portions of the guard apparatus are themselves protectively covered by encasing protective shrouds or housings, thus discouraging disassembly of the guard by vandalism.
A feature of the present invention is that it will substantially encapsulate and cover all of the bolt and nut members of a flanged piping connection at for example, an oil/gas well Christmas tree.
Another feature of the present invention is that it provides a guard apparatus which is difficult to disassemble, and discourages removal of itself by vandalism from an oil or gas well Christmas tree apparatus and thus, discourages or prevents theft of the well Christmas tree itself.